was it built as a bridge to allow traffic/people to cross the road in safety? No

Is it the Queensway Tunnel? No

Pandora is nearest so far, but it's not landslides they're worried about - they're contained by a seperate steel mesh barrier. With a large river running beside the road, what might you see if you looked up?

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"Women who carry a little extra weight tend to live longer than the men who mention it." - Mrs Worrier

It was a popular spot for suicides and the resultant traffic carnage took forever to sort out. The actual spot was the Clifton Suspension Bridge near Bristol. You can see the "tunnel" in the bottom right here

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"Women who carry a little extra weight tend to live longer than the men who mention it." - Mrs Worrier